Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$130.27	13.349%	$147.6597	$147.66	$147.65	$147.70
Purchase #2	$151.53	13.150%	$171.4562	$171.46	$171.45	$171.50
Purchase #3	$152.52	6.110%	$161.839	$161.84	$161.85	$161.80
Purchase #4	$107.37	3.601%	$111.2364	$111.24	$111.25	$111.20
Purchase #5	$156.88	5.846%	$166.0512	$166.05	$166.05	$166.10
Purchase #6	$233.31	13.402%	$264.5782	$264.58	$264.60	$264.60
Purchase #7	$107.95	8.479%	$117.1031	$117.10	$117.10	$117.10
7 purchase totals =	$1,039.83		$1,139.9238	$1,139.93	$1,139.95	$1,140.00